The claim references an instance in where a woman was shot and fortunately survived due to the silicone breast implants in her chest. While there is truth in the fact that the woman was able to survive due to her silicone breast implants, it is not safe to state that silicone breast implants are bulletproof, as the claim can be very misleading due to the fact that silicone itself is not bulletproof.
In a study published by the National Library of Medicine, it is stated that "The impact of a gunshot is tied to a bullet's path and placement within the body.12 The extent of the resulting trauma is influenced by multiple factors, one of which being the physical characteristics of the tissue that has been penetrated.12 Thus, if there is some sort of barrier (eg, bone or implant) to slow or deflect a bullet, it may serve as a protective factor." This means that while the bullet was affected by the silicone and different parts of the patients body, the silicone itself within the breast implant is not bulletproof
In a YouTube video posted by TAOFLEDERMAUS, a test is conducted where different rounds of bullet are shot at a standard silicone breast. in the video we can see that silicone breast implants do affect that trajectory and impact, it is negligible at best so they are in fact NOT bulletproof,
sources
https://pmc.ncbi.nlm.nih.gov/articles/PMC9949879/
https://www.youtube.com/watch?v=qjHn3RPdGIg